This invention relates to an impact driver and, more particularly, to an impact driver which does not rely on an external strike to cause the driver to operate.
Rotary impact drivers are well known. These are used to loosen or tighten fasteners which are stuck or which require significant torque in their operational placement or removal. In these devices, a durable handle houses a spring and a bit holder. A cam drives the bit holder.
When operated, a bit is inserted onto a fastener which may be a Phillips screw, a slotted screw, a hex head or any other rotary fastener for which a bit is provided. The rear end of the handle is struck by a discrete, manually-held mallet or hammer to provide a rotationally directed impact on the fastener. The blow serves to produce a force into the fastener as well as a rotational impact force thereon.
Depending on the size and other parameters of the fastener and its application, such a blow having the force of a discrete hammer or mallet may not be necessary. In many applications, while a rotational impact on the fastener is helpful, it may not require the extreme force of such a blow.
It is thus desirable to provide an impact apparatus which eliminates the necessity of striking an impact tool with a discrete hammer. It is another objective of the invention to provide an impact driver which is capable of imparting a rotational impact to a fastener but without a blow from a discrete hammer.
It is yet a further objective of the invention to provide a self-contained or self-actuating rotary impact driver where manipulation of the tool itself generates the rotational impact without requiring that the tool be struck by a hammer.
To these ends, an impact tool according to the invention includes an internal spring-loaded hammer within the tool. Manual compression of the tool toward a fastener loads the spring until a trigger mechanism releases the hammer to drive a cam housing forwardly and the associated bit holder both into the fastener and rotationally. Thus, a manual, linear pushing motion is converted into a rotational impact force. A manually adjustable screw mechanism is used to provide pre-load adjustment for the hammer spring. Also, a reversing apparatus is operable by manual rotation of the bit housing to reverse the rotary impact direction to selectively create forward or reverse drive direction for the same manual actuating push toward the fastener.
These and other objectives and advantages will become readily apparent from the following detailed description of a preferred embodiment of the invention and from the drawings in which: